1. Field of the Invention
The present invention relates to a solid electrolytic capacitor having an anode lead frame and cathode lead frame with their lower end surfaces exposed from the end surface of the exterior resin.
2. Description of Related Art
Conventionally, capacitors have been widely used in electronic circuits. Among the capacitors, electrolytic capacitors are relatively small and have large-capacity, and therefore, they have been often used in electrical power circuits and the like. As an example, such electrolytic capacitors include a solid electrolytic capacitor having the structure shown in FIG. 17. This solid electrolytic capacitor has a capacitor element having an anode lead-out part 121 and a cathode lead-out part 15. The anode lead-out part 121 and an anode lead frame 161 are connected to each other, while the cathode lead-out part 15 and a cathode lead frame 162 are connected to each other. The solid electrolytic capacitor shown in FIG. 17 has the structure in which parts of the anode lead frame 161 and cathode lead frame 162 and the capacitor element are covered by an exterior resin 19, while exposed parts of the anode lead frame 161 and cathode lead frame 162 from the exterior resin 19 are bent along the peripheral surface of the exterior resin 19.
In forming the solid electrolytic capacitor having the structure described above, when the anode lead frame 161 and the cathode lead frame 162 are bent along the exterior resin 19 as described above, a significant bending stress is applied. Therefore, the exterior resin 19 has to be thick to ensure the strength that can endure the bending stress. However, the thick exterior resin 19 increases the size of the capacitor, and therefore is not preferable. Further, recently there is a growing need for high capacity capacitors and it is required to increase the volume occupied by the capacitor element in the capacitor. To meet such requirements, a solid electrolytic capacitor having the structure shown in FIG. 18 has been proposed and used (see for example Japanese published unexamined patent application No. 2002-367862).
The solid electrolytic capacitor shown in FIG. 18 comprises the flat plate-like anode lead frame 161 and cathode lead frame 162, the lower end surfaces of which are exposed from the exterior resin 19. In such a solid electrolytic capacitor, in the case where the lead wire shown in FIG. 18 is used as the anode lead-out part 121, the anode lead-out part 121 and the cathode lead-out part 15 are not located on the same horizontal level. Therefore, when a conductive member 18 is mounted on the anode lead frame 161 and the anode lead-out part 121 is mounted on the conductive member 18, care should be taken for the capacitor element to be disposed horizontally. However, the thickness of each layer forming a capacitor element varies between individual layers. When such a capacitor element is connected to the anode lead frame 161 and the cathode lead frame 162 so that the cathode lead-out part 15 and the cathode lead frame 162 come into surface contact with each other for strong connection, the anode lead-out part 121 is separated from the conductive member 18 to fail in the reliable connection, leading to the problem of increase in ESR (Equivalent Series Resistance) of the capacitor or generation of defective units. Also, when it is attempted to firmly connect the conductive member 18 and the anode lead-out part 121, the cathode lead-out part 15 is not reliably connected to the cathode lead frame 162, thereby having problems of increase in the ESR and generation of defective units.